Process for making copper-containing oriented silicon steel

ABSTRACT

A grain-oriented silicon steel made by constituting a silicon steel to contain from about 2.2-4.0% silicon and from about 0.240.75% copper, hot rolling it to a thickness of about 0.075-0.1 inches, cold rolling in one cold reduction to a thickness of 0.025 inches or less and then texture annealing for a time sufficient for secondary recrystallization and grain growth to be effected is disclosed.

nite States atent Malagari, Jr.

[ PROCESS FOR MAKING COPPER-CONTAINING ORIENTED SILICON STEEL [75] Inventor: Frank A. Malagari, Jr., Freeport,

[73] Assignee: Allegheny Ludlum llndustries, Inc., Pittsburgh, Pa.

[22] Filed: Oct. 1, 1973 [21] Appl. No.: 402,228

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 229,233, Feb. 11,

1972, abandoned.

[52] U.S. Cl 148/111, 148/3155, 148/112 [51] int. Cl. H011 1/04 [58] Field of Search 148/111, 112, 110, 31.55;

[56] References Cited UNlTED STATES PATENTS 2,209,687 7/1940 Crafts 148/111 2,287,466 6/1942 Carpenter 148/111 1 Mar. 25, 1975 2,561,945 7/1951 Payson 148/112 2,867,557 1/1959 Crede et a1. 148/111 3,008,856 11/1961 Mobios 148/111 3,130,091 4/1964 Carpenter et a1 148/111 3,165,428 l/l965 Albert et a1 148/111 3,671,337 6/1972 Kumai et a1. 148/111 OTHER PUBLICATIONS Kussmann, et 211.; Gekupferter Stahl fur Dynamo-und Transformatorenbleche, in Stahl und Elsen, 1930, pp.

Primary ExaminerWalter R. Satterfield Attorney, Agent, or FirmVincent G. Gioia [57] ABSTRACT A grain-oriented silicon steel made by constituting a silicon steel to contain from about 2.24.0% silicon and from about 0.24-0.75% copper, hot rolling it to a thickness of about 0.075-0.l inches, cold rolling in one cold reduction to a thickness of 0.025 inches or less and then texture annealing for a time sufficient for secondary recrystallization and grain growth to be effected is disclosed.

5 Claims, N0 Drawings PROCESS FOR MAKING COPPER-CONTAINING ORIENTED SILICON STEEL CROSS REFERENCE This application is a continuation-impart of pend- 5 found that when the critical composition limits of copmg Patent application 229,233, filed 1 per are not employed or when the critical process steps 1972 now 9 for preparing the silicon steel in final useful form are not employed, obtaining highly oriented silicon steel BACKGROUND OF THE INVENTION with good permeability and low core losses cannot be A product that has become known as silicon steel is aCcomPllshel, widely used because it can be made with very desirable Although 8 1 Steels X large amounts of magnetic propertiss Silicon steels have high permea sil con, the silicon steels of this inyention are those conbility to magnetic flux and small core losses and are taming from PP 224L098 Preferably therefor very useful in electrical devices involving elec-i l slhcon' There a @knwnshlp between tmmagnetism silicon and copper such that the des rable high permea- Although all silicon steels have good magnetic propp and low Core 1055 cbamqtensnc of an q q erties, the silicon steels with the best magnetic proper- Steel be retameq a process.u.smg a Smgle ties are those that are known as oricnted silicon steels. cold reducuon. .when the crmqal compositions of both Oriented silicon steels have cube-on-edge crystal struc- 2O and slhcon are not In the ranges Set forth ture that is oriented in the direction of rolling. To obherein tain silicon steels with a high degree of orientation, The final mixture antealmg y accomphshed prior art processes require very careful control of the accordance pn.0r an and n at a temper: chemistry of the steel and the sequence of process steps 2 and for a time sultablfi for h spegfic 5 p used to produce it in a thin, flat strip. For example, 3 the alloy Textilrehannea gglg prior art processes required hot reductions of the steel ecte at tlemperatures m t e flange O followed by cold rolling in several reductions with inand preferably at about 2150 termediate anneals to preserve the high permeability DETAILED DESCRIPTION OF THE INVENTION and low core loss character of the silicon steel,

A "5? 2 01351111. 1.153111: ZZZ 53?: 1113333501 accor n e THE INVENTION dance with this invention; however, all were produced This invention is a process for producing grainwith similar conventional steps. The steels were constioriented silicon steels which employs a single cold rolltuted, cast and hot rolled by conventional means to ing step and is accordingly much more economical than thicknesses between 0.075 and 0.1 inches. The hot more extensive processes. rolled band was then treated conventionally to remove The process of this invention includes constituting a scale and heat treated before cold rolling. silicon steel to contain from about 2.20-4.0% silicon The heat treated and descaled steel was then cold and from about 0.240.75% copper. In this specificarolled directly to gauge, i.e. to 0.025 inches or less, tion all compositions are described in terms of percent after which it was texture annealed at 2,150F. by weight of the total composition unless otherwise The copper and silicon content of these steels and specified. The silicon steel is hot rolled to a thickness data obtained from analyzing them are set forth in of from about 0.075-0.1 inches and then cold rolled in Table l. The compositions in Table 1 indicate that all one single cold reduction to a thickness of0.025 inches steels include the critical silicon composition of the or less. The cold rolled strip is then texture annealed present invention, but some contain less than the critifor a time sufficient for secondary recrystallization and cal amount of copper and some contain in excess of the grain growth to be effected. critical amount of copper. The steels of this invention Copper is known to bean ingredient of silicon steel were rolled to four different gauges ranging from the and with the increased usage of scrap, copper is present maximum thickness of the invention, 0.025 inches to a in trace amounts in almost all silicon steels. However, gauge of 0.0108 inches. Specimens of each steel at in the process of the present invention it hasbeen each thickness were analyzed for permeability and core found that a very limited and critical range of copper loss with the exception of two specimens at 0.0108 must be present to obtain the desirable properties from inches which were not suitable for analysis. These data the simplified process that involves a single coldrolling are set forth in the following table.

TABLE 1 Magnetic Quality for Various Gauges .025" .0 85" .014" .0108" WPP at ,u. at WPP at ,u. at WPP at p, at WPP at [.L at Si (C/I) Cu(7z') 15KB 10H 15KB 10H 15KB 10H 15KB 10H 2.50 .0l 1.80 1672 1.26 1620 N 1550 1.25 1460 2.72 .0l 1.33 1731 .97 1729 .93 1580 .98 1511 3.00 .01 1.46 1722 1.03 1692 1.04 1529 1.19 1454 3.20 .0l 1.46 1720 1.00 1690 1.04 1540 1.20 1450 3.20 .15 1.54 1590 1.32 1550 1.04 1530 Magnetic Quality for Various Gauges .025 0108 WPP at p. at WPP at p at WPP at p. at WPP at p. at Si (7() Cu('7c) 15KB 10H KB 10H 15KB 10H 15KB 10H It is evident from the data in Table 1 that alloys containing in excess of 0.75% copper are characterized by large core losses and low permeability compared with the same alloys containing the critical quantity of copper. To a lesser but very definite extent, the alloys having less than the critical quantity of copper also exhibit greater core losses than equivalent alloys containing copper in the critical range.

The more desirable core losses and permeabilities of the alloys of this invention are obtained as the final gauge gets thinner. It is clear from the data that the desirable low core loss and high permeability properties increase rapidly as the thickness of the final cold rolled gauge increases from .0108 inches to 0.025 inches.

In summary, the process of the present invention provides for an economical method for making highly oriented silicon steel, a process employing a single cold rolling step instead of multiple cold rolling steps with intermediate annealing. The process has been demonstrated to depend upon the presence of critical amounts of copper and silicon within the silicon steel and upon cold rolling to a gauge less than 0.025 inches. The process as thus set forth permits obtaining oriented silicon steel with a single cold roll and is therefor a great improvement over prior art processes requiring multiple cold rolling steps with intermediate heat treatments.

It is evident that the usual methods for producing silicon steels conventionally employed will be used in the process of this invention. It is also contemplated that the compositions of silicon steels employed in this invention will include conventionally used materials to provide their own functions and will exclude those materials known to be destructive of the magnetic properties of silicon steels.

What is claimed is:

1. A process for producing grain-oriented silicon steel which comprises:

A. hot rolling a silicon steel consisting essentially of from about 2.20-4.0% silicon and from about 0.240.75% copper to a thickness of from about 0.0750. 10 inches,

B. cold rolling the hot rolled steel in one cold reduction to 0.025 inch thickness or less, and

C. texture annealing the cold rolled steel at a temperature of from about 2,0002,300F and for a time sufficient for secondary recrystallization and grain growth to be effected.

2. The process of claim 1 wherein the steel contains,

about 0.3 to 0.5% copper.

3. The process of claim 1 in which the steel contains between about 2.5 and 3.0% silicon.

4. The process of claim 1 wherein texture annealing is effected at 2,150F.

5. The process of claim 1 wherein said texture annealing is effected for a time sufficient to produce a product having a permeability of at least 1,550 ,u. at 10 H and a 99m lass a o t W @9 K 

1. A PROCESS FOR PRODUCING GRAIN-ORIENTED SILICON STEEL WHICH COMPRISES: A. HOT ROLLING A SILICON STEEL CONSISTING ESSENTIALLY OF FROM ABOUT 2.20-4.0% SILICON AND FROM ABOUT 0.24-0.75% COPPER TO A THICKNESS OF FROM ABOUT 0.075-0.10 INCHES, B. CODL ROLLING THE HOT ROLLED STEEL IN ONE COLD REDUCTION TO 0.025 INCH THICKNESS OR LESS, AND C. TEXTURE ANNEALING THE COLD ROLLED STEEL AT A TEMPERATURE OF FROM ABOUT 2,000*-2,300*F AND FOR ATIME SUFFICIENT FOR SECONDARY RECRYSTALLIZATION AND GRAIN GROWTH TO BE EFFECTED.
 2. The process of claim 1 wherein the steel contains about 0.3 to 0.5% copper.
 3. The process of claim 1 in which the steel contains between about 2.5 and 3.0% silicon.
 4. The process of claim 1 wherein texture annealing is effected at 2,150*F.
 5. The process of claim 1 wherein said texture annealing is effected for a time sufficient to produce a product having a permeability of at least 1,550 Mu at 10 H and a core loss of at most 1.40 WPP at 15 KB. 